1. Technical Field of the Invention
The present invention relates to an electrode generating hydro-dynamic pressure which generates a dynamic pressure in a gap with a grinding wheel by rotation of the grinding wheel for electrolytic dressing grinding.
2. Description of the Related Art
With the recent progress in scientific technique, requirements for superfine processing have been rapidly heightened. As mirror surface grinding means for satisfying the requirements, the present applicant et al. have developed and published an electrolytic in-process dressing grinding method (ELID grinding method) (Riken Symposium "Latest Technique Trend of Mirror surface Grinding" held on Mar. 5, 1991).
In the ELID grinding method, as diagrammatically shown in FIG. 1, instead of an electrode in conventional electrolytic grinding, an electrically-conductive grinding wheel 1 is used, an electrode 2 is disposed opposite to the grinding wheel 1 with a gap therefrom, and an electrically-conductive liquid 3 is passed between the grinding wheel and the electrode to apply a voltage to between the grinding wheel 1 and the electrode 2. During electrolytic dressing of the grinding wheel, a workpiece is ground by the grinding wheel. Specifically, in the grinding method, the metal-bonded grinding wheel 1 is used as an anode, while the electrode 2 opposite to the surface of the grinding wheel with a gap therefrom is used as a cathode. By performing the electrolytic dressing of the grinding wheel simultaneously with grinding operation, the grinding performance can be maintained/stabilized. Additionally, in FIG. 1, numeral 4 denotes a workpiece (material to be ground), 5 denotes an ELID power source, 6 denotes a power supplier, and 7 denotes a nozzle of the electrically-conductive liquid.
In the ELID grinding method, even if abrasive grains are fine, the clogging of the grinding wheel does not occur through the electrolytic dressing of the abrasive grains. By making fine the abrasive grains, a remarkably superior processed surface like a mirror surface can be obtained by the grinding processing. Therefore, it is expected that the ELID grinding method be applied to various grinding processings as means which can maintain the ability of the grinding wheel in an operation ranging from a highly efficient grinding to a mirror surface grinding and which can form in a short time a highly precise surface unable to be formed in the prior art.
In the ELID grinding described above, on the surface of the cathode 2 opposed to the anode of the metal-bonded grinding wheel 1, a characteristic phenomenon is observed that metal components of a grinding wheel bonding material are deposited based on the principle of electric plating, contrary to the electrolytic erosion of the grinding wheel bonding material, i.e., anode reaction. In principle, since the deposits on the cathode surface have a composition close to that of a pure metal, electric conductivity is not lost. However, when the ELID grinding processing is performed for a long time, problems arise: (1) the gap between the cathode and the grinding wheel is filled with the deposits; (2) a sufficient amount of electrolytic liquid cannot be stably supplied; and further (3) air is drawn in the electrode gap to make unstable the electrolytic dressing of the grinding wheel. Therefore, ELID grinding effect cannot be maintained at the time of a continuous unmanned operation, and it has been recognized that the problems should be solved to realize complete automation.